It should have a major effect in VBR mode, with "0" meaning "automatic quality". The sematics of the parameter is silently switched from constant quantisation parameter (qp) in "Constant Quantizer" (constqp) mode to constant quality (cq) in "Variable Bitrate" mode.
Is it supposed to be this way? It has an effect even in VBR mode? Quote from: Urik on December 15, 2020, 07:31:05 PMOne more thing, in Avidemux, for both encoders, in variable bitrate mode, Quality value entry field is now unlocked, which confused me again. Some parts are patched to expose internal, highly sophisticated functions to external usage by Avidemux (very few patches actually modify behaviour). FFmpeg = libavutil + libavcodec + libavformat + libavfilter + libswscale + libpostproc + libavdevice + libavresample + libswresample + a set of command-line frontends to use all of them.Īvidemux bundles libavutil, libavcodec, libavformat, libswscale and libpostproc. Quote from: Urik on December 15, 2020, 07:31:05 PMJust to clarify, when you say libavcodec, it's the same thing that's in FFMPEG, right? If you happen to find some spare time, it would be indeed interesting to determine experimentally whether "slow" on your hardware implies scenecut detection even with lookahead option not specified on the ffmpeg command line. The "slow" preset is definitely slower on my hardware than just "hq" despite no scenecut and no lookahead support, so the encoder is putting more effort in.
The "slow" preset is "hq" + what NVIDIA calls "2-pass" (which is not 2-pass one would think of). I guess this could've been just because I always specified lookahead. With voukoder plugin (ffmpeg-based) and my ffmpeg scripts I just always used "slow" preset so I thought that makes the difference, because I had the auto I-frames. Quote from: Urik on December 15, 2020, 07:31:05 PMI used to think that scene cuts were always on by default, or at least on "better" presets. Quote from: Urik on December 15, 2020, 07:31:05 PMWith lookahead at 0 there were no I-frames placed, then I tried lookahead of 31 and 10, and they were placed exactly where needed.
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